what oil weight should I use ?

I have heard a lot of opinions with no description of motors.
I have a 1993 Mastercraft W/ 351HO 285 HP. I am using Mobil 1, Sythetic.
Can anyone tell me what weight to use. ( From a owners manual maybe )

2002 MC w/ Vortec 351 TBI (315hp)

20W/50 is what the manual calls for.

20W/50 is for regular oil. Synthetic will be different and not in the manual.

i have a 99 MC w/ Vortec TBI, asks for 15w 40

Here is a question I asked on the MC forum

I have a 95 Prostar 205 with 300 hours on it. I'm currently putting 20-50 oil in it. I've heard alot about Mobil 1 synthetic oil. Should I change oil and go to Mobil 1 or keep changing every year with Penzoil 20-50 (recommend). We only put about 60 hours a year on it. If I go to Mobil 1 what type should I get?


Thanks Dave


Answer

Dave,
I have a 1993 Prostar 190 with a Ford 351HO 285HP. I have always run Mobil 1 synthetic oil (0/50). I change my oil & filter every 50 hours and during winterization. My boat runs like a champ. Hope this helps.

I also got a responce from a guy that said he has over 1100 hours on his Ford 351 and he uses Mobil 1 0/30. I can't remember the year but it was between 90 and 93. He also said he has had 0 engine problems.

my Indmar 310hp in my 2000 Supra Launch says 15W40 ...it says it in the maual and right on the oil fill cap on the motor..